1. Field of the Invention
This invention relates to a process of preparing stroma-free hemoglobin solutions.
2. Description of the Prior Art
As is well-known, hemoglobin is the active oxygen transport compound in blood present in erythrocytes. It has long been desirable to obtain hemoglobin in substantially pure form free of stroma and blood enzymes for use as an "in vitro" diagnostic reagent and an "in vivo" blood substitute.
Stroma-free hemoglobin is known. However, complicated processes have been required in order to obtain stroma-free hemoglobin. One problem associated with the production of stroma-free hemoglobin is the conversion of hemoglobin to methemoglobin. This conversion occurs when the iron atom in the heme changes valence from Fe.sup.++ to Fe.sup.+++ due to oxidation. The methemoglobin does not function as a reversible oxygen transport mechanism as does hemoglobin. Thus care must be taken to prevent conversion of hemoglobin to methemoglobin in the purification process.
Several processes have been proposed for preparing stroma-free hemoglobin. Exemplary of such processes are those disclosed in "An Improved Stroma-Free Hemoglobin Solution" by Greenberg et al.; Surgical Forum V. 26, pp. 53-55 (1975); "Further Studies with Stroma-Free Hemoglobin Solution" by Rabiner et al.; Annuals of Surgery, pp. 615-622 (April 1970); "Acute Oxygen Supply by Infusion of Hemoglobin Solutions" by Bonhard; Federation Proceedings V. 34, No. 6, pp. 1466-1467 (May 1975); "Blood Substitute and Blood Plasma Expander Comprising Polyhemoglobin" by Bonsen et al., U.S. Pat. No. 4,001,401; and "Characteristics of Stroma-Free Hemoglobin Prepared by Crystallization" by DeVenuto et al.; J. Lab. Clin. Med., pp. 509-516 (March 1977). None of these methods are satisfactory for large scale production of stroma-free hemoglobin, with reduced methemoglobin formation.
The present invention provides a method of producing stroma-free hemoglobin which is adapted to be used in large scale production. It does not require high speed centrifugation thereby facilitating large scale production. It provides a substantially pure stroma-free hemoglobin which is low in methemoglobin.
These and other advantages are attendant to the invention and will be more fully understood by the following disclosure thereof.